Composition and method for corrosion inhibition utilizing an epoxy resin, an amine curing agent, an alcohol and optionally a hydrocarbon diluent

ABSTRACT

A composition is provided which, when applied to a metal surface, forms a corrosion-inhibiting film thereon. The composition comprises an epoxy resin, an effective amount of a curing agent for the epoxy resin, an alcohol, and a hydrocarbon diluent. The composition is applied by contacting the metal surface with the composition as one solution or as a hydrocarbon solution of the epoxy resin and a solution comprising the alcohol and the curing agent. The composition is particularly useful in the treatment of down-well metal surface in oil and gas wells to inhibit the corrosion of the metal.

This application is a continuation-in-part of application Ser. No.07/657,237, filed Feb. 19, 1991, now U.S. Pat. 5,079,041, which is acontinuation of application Ser. No. 07/430,690, filed Oct. 31, 1989,now U.S. Pat. No. 5,045,359, which is a continuation-in-part of Ser. No.225,662 filed Jul. 22, 1988, now abandoned, which was a continuation ofSer. No. 698,062 filed Feb. 4, 1985, now abandoned, which was adivisional of Ser. No. 465,077 filed Feb. 9, 1983, now U.S. Pat. No.4,526,813, which was a continuation of Ser. No. 369,293 filed Apr. 16,1982, now abandoned, which was a continuation-in-part of Ser. No.181,913 filed Aug. 27, 1980, now abandoned, the texts of all theforegoing applications being incorporated herein by reference.

This invention relates to the treatment of metal surfaces to increasetheir resistance to corrosion. It further relates to compositions whichform a corrosion-resistant film on metal surfaces to which they areapplied.

The problem of corrosion of metal surfaces in contact with air and wateris well known. Corrosion and pitting are accelerated in environments inwhich metal surfaces are in contact with chemicals such as hydrogensulfide, carbon dioxide and organic acids, and water having a highelectrolyte concentration. Such environments are typical of down-wellconditions in oil and gas wells, in which corrosion of metal pipes,pumps and other equipment poses a serious problem requiring monitoringof well sites, frequent maintenance and costly replacement of parts. Oilrecovery operations in deep-sea oil fields present these corrosionproblems in their most extreme form. The down-well metal surfaces are incontact with large quantities of corrosive chemicals such as dissolvedacid gases present in the recovered oil, and in addition, the metalsurfaces are subjected to temperatures of 250° F. or higher andpressures of 3000 psig or higher, the extreme conditions of temperatureand pressure acting to accelerate corrosion and to intensify theproblems of applying and maintaining chemical protection for theequipment. In offshore oil wells, secondary recovery operationsinvolving water-flooding of the undersea formations subjects thedown-well equipment to highly corrosive sea water containing dissolvedoxygen.

Conventional corrosion-inhibiting agents are often not effective at allunder such extreme conditions or reduce corrosion significantly for onlya short period of time and then must be reapplied, often at greatexpense and inconvenience if the well site is not easily accessible or,as in the case of off-shore wells, poses difficulties of transportingand applying large volumes of chemicals.

It is therefore an object of this invention to provide a compositionwhich can be applied to a metal surface to inhibit corrosion and pittingon the metal. It is a further object of the invention to provide amethod of treating metal surfaces so as to form a film which inhibitscorrosion on the metal even under extreme conditions of temperature andpressure and in highly corrosive environments. It is a further object ofthe invention to provide an article having a surface film of acomposition which inhibits corrosion.

SUMMARY OF THE INVENTION

According to the invention, there is provided a composition which, whenapplied to a metal surface, forms a corrosion-inhibiting film on themetal surface, the composition comprising an epoxy resin, an effectiveamount of an amine curing agent for the epoxy resin, an alcohol, and ahydrocarbon diluent. The composition can be applied by contacting themetal surface with the composition so that a film is formed thereon. Thecomposition can be applied as one solution or by sequentially contactingthe metal with a hydrocarbon solution of the epoxy resin and ahydrocarbon solution of the alcohol and curing agent. Also according tothe invention, metal articles having a corrosion-inhibiting film thereonare provided.

DETAILED DESCRIPTION OF THE INVENTION

Any epoxy resin having, on the average, more than one vicinal epoxidegroup per molecule can be used in the invention composition and process.The epoxy resin may be saturated or unsaturated, aliphatic,cycloaliphatic, aromatic or heterocyclic, and may bear substituentswhich do not materially interfere with the curing reaction. They may bemonomeric or polymeric.

Suitable epoxy resins include glycidyl ethers prepared by the reactionof epichlorohydrin with a compound containing a hydroxyl group carriedout under alkaline reaction conditions. The epoxy resin productsobtained when the hydroxyl group containing compound is bisphenol A arerepresented below by structure I wherein n is zero or a number greaterthan 0; commonly in the range of 0 to 10, preferably in the range of 0to 2. ##STR1##

Other suitable epoxy resins can be prepared by the reaction ofepichlorohydrin with mononuclear di- and tri-hydroxy phenolic compoundssuch as resorcinol and phloroglucinol, selected polynuclear polyhydroxyphenolic compounds such as bis(p-hydroxyphenyl)methane and4,4'-dihydroxy biphenyl, or aliphatic polyols such as 1,4-butanediol andglycerol.

Epoxy resins suitable for use in the invention have molecular weightsgenerally within the range of 50 to about 10,000, preferably about 200to about 1500. The commercially available Epon 828 epoxy resin, areaction product of epichlorohydrin and 2,2-bis(4-hydroxyphenyl)propane(bisphenol A) and having a molecular weight of about 400, an epoxideequivalent (ASTM D-1652) of about 185-192, and an n value in structure Iabove of about 0.2, is presently preferred because of the superioreffectiveness, as shown in field tests, of the invention compositioncontaining Epon 828.

Additional epoxy-containing materials suitable for use in the presentinvention include the epoxidized derivatives of natural oils such as thetriesters of glycerol with mixed long-chain saturated and unsaturatedacids which contain, e.g., 16, 18 and 20 carbon atoms. Such natural oilsare represented by formula II: ##STR2## wherein R represents alkyland/or alkenyl groups containing 15 to 19 carbon atoms with the provisothat epoxidation of said oils yields a polyepoxide having more than onevicinal epoxy group per molecule of epoxidized oil. Soybean oil is atypical triglceride which can be converted to a polyepoxide suitable foruse in the instant invention.

Other polyepoxides suitable for use in the present invention are derivedfrom esters of polycarboxylic acids such as maleic acid, terephthalicacid, oxalic acid, succinic acid, azelaic acid, malonic acid, tartaricacid, adipic acid and the like with unsaturated alcohols as described byformula III: ##STR3## wherein Q represents a valence bond, or thefollowing groupings: 1,2-phenylene, 1,4-phenylene, methylene,dimethylene, trimethylene, tetramethylene, pentamethylene,hexamethylene, heptamethylene, vinylene, 1,2-cyclohexylene,1,4-cyclohexylene, 1,2-ethylenediol and the like, and R' representsalkylene and branched alkylene groups containing 4 to 14 carbon atoms.Representative epoxidized esters derived from materials described bystructure (III) include the following:di(2,3-epoxybutyl)tetrahydrophthalate, di(2,3-epoxyoctyl)oxalate,di(2,3-epoxyisobutyl)adipate, di(3,4-epoxypentyl)succinate,di(4,5-epoxydodecyl)terephthalate, di(3,4-epoxyhexyl)phthalate,di(2,3-epoxybutyl)tartrate, di(7,8-epoxytetradecyl)adipate,di(3,4-epoxybutyl)glutarate, di(2,3-epoxyhexyl)pimelate,di(3,4-epoxyoctyl)suberate, di(4,5-epoxydecyl)azelate,di(2,3-epoxyisohexyl)tetrahydroterephthalate and the like.

In addition to the foregoing, it is contemplated that suitablepolyepoxides can be derived from esters prepared from unsaturatedalcohols and unsaturated carboxylic acids described by formula IV:##STR4## wherein R" represents alkenyl and cycloalkenyl groupscontaining 4 to 12 carbon atoms and R"' represents alkenyl andcycloalkenyl groups containing 4 to 12 carbon atoms. Representativeepoxidized esters include the following:2,3-epoxypentyl-3,4-epoxybutyrate; 2,3-epoxybutyl-3,4-epoxyhexanoate;3,4-epoxyoctyl-2,3-epoxycyclohexane carboxylate;2,3-epoxydodecyl-4,5-epoxyoctanoate;2,3-epoxyisobutyl-4,5-epoxydodecanoate;2,3-epoxycyclododecyl-3,4-epoxypentanoate;3,4-epoxyoctyl-2,3-epoxycyclododecane carboxylate and the like.

Other unsaturated materials which can be epoxidized to give resinssuitable for use in the instant process include butadiene based polymerssuch as butadiene-styrene copolymers, polyesters available asderivatives of polyols such as ethylene glycol with unsaturated acidanhydrides such as maleic anhydride, and esters of unsaturatedpolycarboxylic acids. Representative polyepoxides derived from thelatter include the following: dimethyl 3,4,7,8-diepoxydecanedioate;dibutyl 3,4,5,6-diepoxycyclohexane-1,2-carboxylate; dioctyl3,4,7,8-diepoxyhexadecanedioate; diethyl5,6,9,10-diepoxytetradecanedioate and the like.

Dimers of dienes such as 4-vinyl cyclohexene-1 from butadiene anddicyclopentadiene from cyclopentadiene can be converted to epoxidizedderivatives which are suitable for use in the instant process.

Any agent suitable for curing epoxy resins may be used in the inventioncomposition and method. Curing agents for epoxy resins include amines,acids, anhydrides and aldehyde resins. The curing agent is used in anamount effective for curing the amount of epoxy resin used.

Curing agents suitable for use in the invention composition and processinclude compounds having amino hydrogen atoms. These include aliphatic,cycloaliphatic, aromatic and heterocyclic amines. Examples of curingcompounds include aliphatic polyamines such as ethylene diamine,diethylene triamine, triethylene tetramine, tetraethylene pentamine,1,4-aminobutane, 1,3-diaminobutane, hexamethylenediamine,3-(n-isopropylamino)propylamine, N,N'-diethyl-1,3-propanediamine,hexapropyleneheptamine, penta(1-methyl-propylene)hexamine,tetrabutylenepentamine, hexa-(1,1-dimethylethylene)-heptamine,di(1-methylbutylene)triamine, pentaamylenehexamine,tri(1,2,2-trimethylethylene)tetramine,tetra(1,3-dimethylpropylene)pentaminepenta(1,5-dimethylamylene)hexamine, 5-methylnonanediamine,penta(1,2-dimethyl-1-isopropylethylene)hexamine andN,N'-dibutyl-1,6-hexanediamine.

A class of polyamines particularly suitable for use in the invention areN-alkyl- and N-alkylenyl-substituted 1,3-diaminopropanes and mixturesthereof. Examples of such polyamines includeN-hexadecyl-1,3-diaminopropane, N-tetradecyl-1,3-diaminopropane,N-octadecyl-1,3-diaminopropane, N-pentadecyl-1,3-diaminopropane,N-heptadecyl-1,3-diaminopropane, N-nonadecyl-1,3-diaminopropane, andN-octadecenyl-1,3-diaminopropane. Various commercially availablemixtures of N-alkylated and N-alkenylated diamines can be used in theinvention. The presently preferred polyamine is a commercial productsold under the trademark Duomeen T. This product isN-tallow-1,3-diaminopropane in which the majority of the tallowsubstituent groups are alkyl and alkenyl containing from 16 to 18 carbonatoms each, with a minority of substituent groups having 14 carbon atomseach. It is presently believed that the effectiveness of Duomeen T inthe corrosion-inhibiting composition stems from its relatively highmolecular weight, which produces a long-chain "net" to cover the metalsurface, its polyfunctionality, and its relatively high boiling point,which permits its use in high-temperature environments. Othercommercially available materials include N-coco-1,3-diaminopropane whichthe majority of the coco substituent groups contain 12 to 14 carbonatoms, commercially available under the tradename Duomeen C, andN-soya-1,3-diaminopropane, which contains C₁₈ alkenyl groups along witha minor proportion of C₁₆ alkyl groups.

And surprisingly it has also been discovered that monoamines such ascoco and tallow amines are also very effective in producing corrosioninhibiting compositions. Cocoamines as discussed above contain cocosubstituent groups which are alkyl and/or alkenyl groups, containingfrom 12 to 14 carbon atoms each and is commercially available under thetradename Armeen C (C₁₂ H₂₅ NH₂). Tallowamines also discussed abovecontain tallow substituent groups which are alkyl and/or alkenyl,containing from 16 to 18 carbon atoms each, with a minority ofsubstituent groups containing 14 carbon atoms each.

Additional polyamines suitable for use in the invention can contain 3 ormore nitrogen atoms as illustrated by the following examples:N-dodecyl-diethylenetriamine, N-tetradecyl-diethylene triamine,N-tetradecyl-dipropylenetriamine, N-tetradecyl triethylene tetramine andthe corresponding N-alkenyl triamines.

Other curing agents which can be used include polyfunctionalnitrogen-containing compounds such as, for example, amino acids, aminoalcohols, amino nitriles, and amino ketones; sulfonic acids; carboxylicacids; and organic anhydrides.

Alcohols suitable for use in the invention include any alkanolscontaining at least one -OH functional group. These include alcoholscontaining 1 to about 15 carbon atoms such as methanol, ethanol,1-propanol, 2-propanol, butanols, pentanols, hexanols, heptanols,octanols, 1-pentadecanol, and mixtures of these. The most suitablealcohols include alcohols selected from the group consisting ofmethanol, ethanol, 1-propanol, 2-propanol, n-butanol, n-pentanol,n-hexanol, n-heptanol and combinations of any two or more thereof.Polyols containing 1 to 5 carbon atoms such as ethylene glycol,1,3-propanediol, 2,3-butanediol, glycerol and pentaerythritol can alsobe used. Presently, methanol is preferred, particularly in ananti-corrosion composition containing xylene as the aromatic hydrocarbondiluent, Epon 828 as the epoxy resin, and Duomeen T as the polyamine,because Duomeen T is soluble in methanol at room temperature and becauseof the effectiveness of the resulting corrosion inhibiting system.

A hydrocarbon diluent is used for the invention composition. Examples ofhydrocarbon diluents suitable for use in the treating agents include theisomeric xylenes, toluene, benzene, naphtha, cyclohexylbenzene, fueloil, diesel oil, heavy aromatic oils, Stoddart solvent, crude oil, andcondensate from gas wells. Presently, xylene is the preferredhydrocarbon diluent because it is an effective solvent for the otherpreferred components and because of the corrosion-inhibitingeffectiveness of the resulting composition.

The higher-boiling aromatic hydrocarbons are particularly useful fordeeper wells with higher downhole temperatures and in high-temperaturegas and oil wells generally.

In some treatment methods, discussed below, it is advantageous to employa carrier liquid or drive fluid to force a slug of thecorrosion-inhibiting composition down into the well being treated. Anyof the hydrocarbons listed above as suitable diluents may be used. Forpractical and economic reasons, diesel oil, sea water or condensate fromthe well being treated are preferred carrier fluids.

Various alcohol-aromatic hydrocarbon azeotropes can be used in theinvention compositions to supply at least partially the diluent and thealcohol components. Representative azeotropes include the following,with the weight percent of each component in parenthesis: methanol(39.1)/benzene (60.9); ethanol (32)/benzene (68); 2-propanol(33.3)/benzene (66.7); 1-propanol (16.9)/benzene (83.1); isobutylalcohol (9.3)/benzene (90.7); 1-butanol (68)/p-xylene (32); 2-pentanol(28)/toluene (72) and hexanol (13)/p-xylene (87). It is alsocontemplated that impure alcohol streams such as mixed butanolsresulting from Oxo technology using propylene feedstock can be used inthe treating compositions.

The components of the corrosion-inhibiting system can be mixed in anyorder, but it is presently preferred to dissolve the epoxy resin in ahydrocarbon and add an amine/alcohol/hydrocarbon mixture to thissolution. A batch of the treating composition can be prepared by mixinga first solution of alcohol, hydrocarbon and amine in, for example,approximately a 1:1:1 (mL:mL:g) ratio and a second solution of an epoxyresin in a hydrocarbon in about a 3:1 (g:mL) ratio. Thecorrosion-inhibiting agent is then prepared by mixing the first andsecond solutions in such proportions that the weight ratio of polyamineto epoxy resin in the final solution varies over the broad range ofabout 1000:1 to 1:500, preferably about 100:1 to 1:50, and mostpreferably about 10:1 to 1:5. The weight percent of alcohol in the finalcomposition varies over the broad range of 1 to 99, preferably 10 to 60,and most preferably 20 to 30. The hydrocarbon diluent can be present inany concentration range in which the invention composition remains in anessentially fluid pumpable state.

In laboratory runs and field tests, it has been found that a highlyeffective composition for the treatment of downhole metal surfaces ofoil wells is one having an excess of the amine with respect to theepoxy. A particularly suitable composition for such a highly corrosiveenvironment contains an equivalent ratio of polyamine to epoxy ofgreater than about 1:1, preferably about 1.25:1 to 10:1, most preferablyabout 1.5:1 to 5:1. The protective film obtained with such an amine-richsystem generally has, in contrast to the hard coatings obtained withconventional cured epoxy systems, a tacky, comparatively softconsistency.

The polyamine:epoxy molar ratio corresponding to the preferredequivalent ratios above depends, of course, on the relative number offunctional groups of the specific compounds used, and these ratios canbe computed by methods known in the art. For example, for a polyaminecontaining 3 active hydrogen atoms and an epoxy resin having an averageof 2 epoxide groups per molecule, the stoichiometric molar ratio ofpolyamine:epoxy resin is 0.67:1. The preferred compositions containingsuch polyamines and epoxy resins have a molar ratio of at least about0.8:1, preferably within the range of about 1.1:1 to 10:1, mostpreferably about 1.25:1 to 6:1. The corresponding volume amounts for thepreferred components, based upon a density of about 0.821 g/mL andmolecular weight of 350 for the polyamine and about 1.164 g/mL and 400for the epoxy resin, are generally at least about 1.0:1, preferablyabout 1.3:1 to 12:1, most preferably about 1.5:1 to 7:1.

Although compositions having an extremely large excess of amine areeffective corrosion inhibitors, such compositions have the disadvantageof low durability in extremely corrosive environments such as downwellsurfaces. By contrast, the invention compositions have high corrosioninhibition effectiveness over an extended period of time, reducingcosts, in terms of time, money, equipment failures, and the necessity offrequent reapplication under the severe conditions of off-shore platformwells.

The invention composition is useful for coating oxidizable metalsurfaces, particularly surfaces of objects made from iron and steel. Itis particularly useful for treating metal surfaces such as metal pipesand casings in oil, gas and geothermal wells, which are subjected tohigh temperatures and pressures and corrosive chemical agents.

Down-well treatments with the corrosion-inhibiting compositions can beeffected by a variety of methods depending upon the particular chemicaland physical characteristics of the well being treated. When treatingmetal surfaces, particularly in down-well applications, thecorrosion-inhibiting composition can be applied as one solution, oralternatively it can be applied by contacting the metal surfacessequentially with a solution of the curing agent and a solution of theepoxy resin. In practice, the resin solution and amine solution can bepumped from separate storage tanks to a static mixer at a T-junctureimmediately prior to pumping the mixture downhole. The followingdown-well treatment methods can be used to apply the composition tometal surfaces of equipment used to recover natural fluids from asubterranean reservoir.

Batch Treatment. The invention composition comprising alcohol, epoxyresin, curing agent and hydrocarbon diluent is introduced preferably inan oil carrier into the annulus of a cased wellbore between the casingand the tubing. The well is returned to production and the injectedcompositions are gradually returned with the produced fluids, effectingen route the coating of contacted metal surfaces with acorrosion-resistant film. Alternatively in this method, a liquid columnof the treating agent can be placed in the tubing or the annular spaceand allowed to stand for a time which can range from 10 minutes to 24hours before resuming production, usually at least 2 hours.

Extended Batch Treatment. The invention composition is injected into theannular space of a cased wellbore, the well is closed off, and thecomposition is continuously circulated with well fluids down the annulusand up the tubing for an extended period of time which can vary widelybut will usually be between 6 and 48 hours. At the end of the determinedtime period, the well is returned to production.

Squeeze Treatment. The invention composition is injected down a casedwellbore penetrating a subterranean formation and is forced into theformation against formation pressure with high-pressure pumps. Thecomposition can be injected within a gelled or dispersed polymer matrixbased, for example, on polyacrylamides, biopolysaccarides, or celluloseethers. After the pressure is released, the treating agent is slowlyproduced back with the recovered fluids, resulting in the application ofa corrosion-resistant film on metal surfaces contacted by the treatingagent as it flows to the surface. This method is particularly suitablein high-pressure gas or oil wells.

Spearhead Treatment. A highly concentrated slug of the inventioncomposition, for example about 27 weight percent alcohol, about 27weight percent amine, about 15 weight percent epoxy resin, about 31weight percent hydrocarbon diluent, is injected into the tubing of acased borehole and pressured down the tubing with a fluid column of abrine solution such as 2 weight percent aqueous potassium chloride. Whenthe pressure is released, the aqueous brine column and thecorrosion-inhibiting composition are produced up the tubing. Thecomposition as a concentrated slug thus contacts the metal walls of thetubing and lays down a protective film as it flows in a downward andupward circuit.

Metal surfaces can also be protected by dipping or spraying the surfaceswith the invention compositions and then allowing excess fluid to drainfrom the treated surfaces at ambient conditions. A protective film isthus formed on the metal surface without conventional heat-curing orextended air-drying treatment, although such drying treatments can beused if desired and if conditions permit it. The advantage in using ananti-corrosion system which does not require air- or heat-drying is thatthe system can be applied to metal surfaces which are hundreds orthousands of feet below ground level or are in an environment which isalways flooded with brine or other fluids.

When applying the composition to the metal tubing of, for example, a gasor oil will, it is not necessary to pre-coat the treated metal surfaceswith oil or other substances prior to applying the inventioncomposition, and the treated surfaces may or may not have an oil coatingprior to the application. The invention has been found effective ininhibiting corrosion in wells producing as much as 95 percent brine and5 percent oil.

The nature of the film thus formed can vary according to the particularcomposition used and the environment in which it is applied, but it hasbeen found that the film will generally be a soft, sticky layer adheringto the metal surface. It is not necessary that the composition harden toa tough coating, and it has been found in laboratory runs that theapplied film tends to maintain a tacky or greasy consistency.

EXAMPLE I

This example describes the treatment of an open-ended cased borehole inthe North Burbank field in Oklahoma to inhibit corrosion on metalsurfaces of the down-well equipment. The test well was a low fluid levelwell producing about 550 barrels of water per day (bwpd) and 4-5 barrelsof oil per day (bopd).

A solution of xylene, methanol and amine curing agent was mixed with axylene solution of an epoxy resin to give a total of 25 gallons of theinvention treating composition. The final composition was 27 weightpercent methanol, 27 weight percent Duomeen T curing agent, 15 weightpercent Epon 828 epoxy resin, and 31 weight percent xylene.

The 25 gallons of inhibitor solution were poured into the annulus of theclosed well. The fluids were circulated through the tubing and annulusfor about 24 hours in an extended batch treatment. The well was returnedto production and the corrosion rate was monitored by a conductivityprobe for a period of 54 days. Prior to injection of the inventioncomposition, the rate of corrosion was about 3.6 mils per year (mpy).During the subsequent 53-day period, the corrosion rate dropped andstayed below the target rate of 0.5 mpy. The iron count measurements inthe produced water decreased from 33 ppm initially to about 24 ppm andremained at that level.

After 53 days, the corrosion rate had increased to 0.5 mpy, where itremained for 3 days. The well was then retreated with a 5-gallon batchof the same corrosion-inhibiting composition. The same extended batchtreatment was used, except that the fluids were circulated for 6 hoursinstead of 24 hours. Following this retreatment, the corrosion rateremained in the range of 0.1 to 0.45 mpy for 21 days.

In an alternate method of treatment using the same composition, a5-gallon batch of the invention corrosion inhibitor was poured directlyinto the annulus and flushed for five minutes without shut-in forcirculation of the fluids. The corrosion rate remained below 0.5 mpy forabout one week, after which the well was retreated by the same method.Two weeks later, when the testing ended, the corrosion rate was 0.1,confirming the effectiveness of the invention corrosion inhibitor in abatch treatment operation.

Prior to the testing of the invention composition, a commerciallyavailable, long-chain, high-boiling amine corrosion inhibitor had beenused. The treatment program consisted of flushing eleven gallons of thecommercial corrosion inhibitor into the annulus initially and thenretreating with five quarts every four days to control corrosion. Theinvention composition was considerably more efficient in terms of itseffectiveness in controlling corrosion rate over an extended period oftime than was the commercial inhibitor.

EXAMPLE II

This example describes the treatment of an open-ended cased borehole inthe North Burbank field in Oklahoma to inhibit corrosion on down-holemetal surfaces. The test well was a high fluid level well producingabout 1250 bwpd and 6 bopd.

A solution of xylene, methanol and Duomeen C curing agent was mixed witha xylene solution of Epon 828 epoxy resin to give a total of 15 gallonsof a composition containing 31 weight percent xylene, 27 weight percentmethanol, 27 weight percent Duomeen T and 15 weight percent Epon 828.

The 15 gallons of inhibitor solution were poured into the annulus of theclosed well. The well fluids and inhibitor were circulated through thetubing and annulus for 24 hours in an extended batch treatment process.The well was returned to production and the corrosion rate was monitoredby a conductivity probe for a period of about two weeks. During thistime the corrosion rate was generally greater than the target rate of0.5 mpy. A subsequent treatment with an additional 15-gallon batch ofthe Duomeen C-containing inhibitor failed to reduce the corrosion rateto this level over a 7-day period. The corrosion rate was 3.5 mpy whenthe inhibitor composition of Example I (containing Duomeen T curingagent) was applied to this well.

A 15-gallon volume of the Duomeen T-containing composition described inExample I was placed in the test well and circulated for 24 hours. Thecorrosion rate decreased from 3.5 mpy to about 0.1-0.2 mpy and remainedbelow the target level of 0.5 for a period of about 98 days. Iron countduring this time remained in the range of 14-17 ppm. Previously in thiswell, it was necessary to apply a commercial inhibitor in an initial11-gallon treatment and follow every four days with 7-quart treatments.This result demonstrates the efficiency and effectiveness of thexylene/Duomeen T/methanol/Epon 828 system in reducing the corrosion ratein cased oil wells. It also demonstrates the necessity of determiningthe appropriate corrosion inhibitor solution for each well or set ofwell conditions. A composition containing Duomeen C was an effectivecorrosion inhibitor in the laboratory under simulated well conditions,but did not perform effectively under the conditions encountered in thisparticular test well using the extended batch treatment method.

EXAMPLE III

This example describes the use of the invention composition for reducingthe corrosion rate in a hot gas condensate well in the Parcperdue Field,Lafayette Parish, La. The well was a hot (about 256° F.) gas condensatewell producing about 7.2 MMcfd gas containing 1 percent carbon dioxide,3 bwpd and 400 bpd condensate. The well depth was 13,266 feet and thewellhead pressure was 6000 psig.

A total of 72 barrels of the invention composition in a carrier of heavyaromatic oil was pumped into the well. The injected fluid contained 2.2weight percent methanol, 2.2 weight Duomeen T curing agent, 1.2 weightpercent Epon 828 epoxy resin, 2.5 weight percent xylene, and 91.9 weightpercent heavy aromatic oil. After the tubing was filled with the fluid,the well was shut in for about 1.5 hours. The inhibitor fluid was thenreturned to the surface and production was resumed.

Prior to this treatment the iron level was 195 ppm, but two days afterthe treatment the iron count had dropped to 56 ppm. The iron level thengradually increased and reached a level of 92 ppm eleven days aftertreatment. At the end of about 30 days after treatment, the iron levelhad reached 200 ppm and a retreatment was carried out using the portionof the original solution which had been returned to the surface duringthe initial treatment. An additional 4.6 volume percent of the inventioncomposition was added and 72 barrels of this mixture was pumped into thewell, the treatment method being the same except that the residence timewas increased from 1.5 hours to 24 hours. The iron concentrationdecreased to 56 ppm but then gradually increased to 101 ppm over a23-day period and remained at this level for seven days. At this time itwas decided to use a spearhead treatment method on the well as describedbelow.

Six and one-half barrels of a concentrated solution of the inventioncomposition containing 27 weight percent methanol, 27 weight percentDuomeen-T, 15 weight percent Epon 828 and 31 weight percent xylene wereinjected into the well followed by 66 barrels of 2 weight percentaqueous potassium chloride solution. This volume was designed to fillthe tubing to within about 300 feet of the well bottom and avoidinjection of the chemicals into the formation. The well was shut in forabout 1.5 hours and then returned to production. The initial ironconcentration in the produced water dropped from 100 ppm to 54 ppm in 12days. The iron count remained in the range of 42 to 55 ppm over a periodof 37 days.

EXAMPLE IV

A series of laboratory corrosion inhibition tests were carried out in1-liter Erlenmeyer flasks equipped with magnetic stirring bars, underlaboratory conditions designed to simulate corrosive oil-waterenvironments encountered in field drilling sites. A charge of 50 mL ofcrude oil and 950 mL of synthetic brine was used in each run. A slowstream of carbon dioxide was bubbled through the solution during eachtest to maintain the mixture near saturation with CO₂ at ambientconditions. After charging 950 mL of synthetic North Sea water (93.1 gCaCl₂ 2H₂ O, 46.4 g MgCl₂ 6H₂ O and 781.1 g NaCl per 5 gal. distilled H₂O) into the Erlenmeyer flask, the resin/hydrocarbon solution andamine/alcohol/hydrocarbon solution were individually charged to theflask, then the specified crude oil was added. The rate of corrosion andpitting index were determined using a Corrater® monitoring systemavailable from Rohrback Instruments. A carbon steel probe was suspendedin the stirred oil-water mixture maintained at approximately 49° C.during each run.

In a typical run, individual mixtures of 1:1:1 by weight samples ofamine/alcohol/hydrocarbon and 3:1 by weight samples of resin/hydrocarbonwere prepared. For these laboratory runs, it was convenient to make afirst solution of 1 g Duomeen T, 1 g methanol and 1 g xylene, and asecond solution of 3 g Epon 828 and 1 g xylene. Specified aliquots ofthese solutions were then transferred to the oil-water mixture containedin the 1-L Erlenmeyer flasks. The corrosion rate and pitting index wereobserved after various reaction times. Results of the tests aresummarized in Table I.

                  TABLE 1                                                         ______________________________________                                             Sol. A.sup.a                                                                          Sol. R.sup.b                                                                          Crude Reaction                                                                              Corrosion                                                                             Pitting                            Run  (g)     (g)     Oil   Time (hrs)                                                                            Rate (mpy)                                                                            Index                              ______________________________________                                        1    0.63 g  0.158 g Tore   3      0.04    0.00                               2    0.6.sup.c                                                                             0.1.sup.d                                                                             NBU.sup.e                                                                           21      0.07    0.00                               3    0.42.sup.f                                                                            0.158   Tor    3      2       1.5                                4    0.32    0.079.sup.g                                                                           Tor    5      0.16    0.10                                                          21      0.1     0.05                               5    0.22.sup.h                                                                            0.079   Tor.sup.m                                                                            5      2.0     0.6                                                           21      0.25    0.1                                6    0.2.sup.i                                                                             0.05.sup.j                                                                            Te.sup.k                                                                            21      0.02    0                                  7    0.2.sup.i                                                                             0.05.sup.j                                                                            NBU.sup.e                                                                           21      0.1     0                                  ______________________________________                                         .sup.a Solution A represents the amine/alcohol/hydrocarbon mixture.           .sup.b Solution R represents the resin/hydrocarbon mixture.                   .sup.c A 0.6 mL aliquot of solution A was used in this run.                   .sup.d A 0.6 g sample of Epon 828 was used as solution R.                     .sup.e NBU represents North Burbank Unit crude oil used with NBU brine        (96.3 g MgCl.sub.2 6H.sub.2 O, 289.2 g CaCl.sub.2 2H.sub.2 O, 1259 g NaCl     in 5 gal. distilled H.sub.2 O).                                               .sup.f This solution contained no methanol (0.21 g Duomeen T and 0.21 g       xylene).                                                                      .sup.g An additional gram of methanol was added to this mixture.              .sup.h This solution contained no methanol (0.11 g Duomeen T and 0.11 g       xylene).                                                                      .sup.i A 0.2 mL aliquot of a solution containing 1/3 amine and 2/3 (70%       xylene and 30% isopropanol) was used.                                         .sup.j A 0.05 mL aliquot of a solution containing 75% resin and 25% xylen     was used.                                                                     .sup.k Te represents Teesside crude oil used with synthetic North Sea         water.                                                                        .sup.l Tor crude oil used with synthetic North Sea water.                

The runs in Table I demonstrate the effectiveness of the inventionalcohol-containing compositions for inhibiting corrosion in systemscontaining Tor crude oil (Runs 1 and 4) and North Burbank crude oil (Run2) using methanol as the alcohol. Runs 3 and 5 show the reducedeffectiveness of the amine/hydrocarbon/resin system in the absence of analcohol. Runs 6 and 7 demonstrate the effectiveness of the inventionisopropanol-containing compositions for inhibiting corrosion in systemscontaining Teeside crude oil and North Burbank Unit crude oil,respectively.

EXAMPLE V

This example provides a hypothetical method of treatment for anoff-shore oil well having a depth of about 15,000 feet, formationtemperatures of 300° F. or higher, and pressures on the order of 5000psig. An amine solution containing equal parts by weight of xylene,methanol and Duomeen T and a solution containing 3 parts by weight ofEpon 828 and 1 part by weight of xylene are used in the ratio of 4 partsby volume of the amine solution to 1 part by volume of the epoxysolution. The solutions are combined in a static mixer at a T-junctionbefore injection into the well. Two barrels of the inhibitor solutionare injected for each 5000 feet of 37/8" I.D. tubing. The injection ofinhibitor solution is followed with 10 to 15 barrels of formation wateror fresh water. The inhibitor is displaced down the tubing with dieseloil as far as practical without injecting inhibitor into the formation,and the well is then shut in for about three hours. The well is returnedto normal production while 50 to 100 ppm of an emulsion-breaking such asNalfloc VH35E is injected into the produced fluids upstream of thecondensate storage tank or separator. This emulstio-breaking treatmentmay be necessary to prevent the formation of an emulsion orhighly-condensed product, presumably caused by injection of an excess ofthe concentrated inhibitor solution.

EXAMPLE VI

The runs in Table II demonstrate the effectiveness of invention systemscontaining Duomeen C as the polyamine curing agent. Duomeen C isdescribed by the general formula R'NH(CH₂)₃ NH₂ wherein R' representsstraight chain hydrocarbon radicals containing on the average 12 to 14carbon atoms. The laboratory runs were carried out as described inExample IV.

                  TABLE II                                                        ______________________________________                                             Sol. A.sup.a                                                                          Sol. R.sup.b                                                                          Crude Reaction                                                                              Corrosion                                                                             Pitting                            Run  (g)     (g)     Oil   Time (hrs)                                                                            Rate (mpy)                                                                            Index                              ______________________________________                                         8   0.45    0.13    NBU.sup.c                                                                           21      0.25    0.11                                9   0.60    0.17    Tor.sup.d                                                                           22.5    0.25    0.1                                10   0.45    0.13    Tor.sup.d                                                                           18      0.05    0.01                               11   None.sup.e                                                                            None.sup.e                                                                            Tor.sup.d                                                                           22.5    0.45    0.2                                ______________________________________                                         .sup.a Solution A was prepared by mixing equal weights of xylene, methano     and Duomeen C.                                                                .sup.b Solution R was prepared by mixing 10 parts by weight of Epon 828       with 3 parts by weight of xylene.                                             .sup.c NBU represents North Burbank Unit crude oil used with NBU brine. A     50 mL sample of oil was used with 950 mL of brine.                            .sup.d Tor represents Tor crude oil used with synthetic North Sea water.      .sup.e In run 11 0.2 g of KP 2023 (a commercial inhibitor from Tretolite      Corp.) was used.                                                         

EXAMPLE VII

The runs in Table III demonstrate the effectiveness of inventive systemscontaining varying ratios of the resin/hydrocarbon solution (Solution R)and the amine/alcohol/hydrocarbon solution (Solution A). Duomeen T wasused as the polyamine curing agent. Duomeen T is described by thegeneral formula R₂ NH(CH₂)₃ NH₂ wherein R₂ represents straight chainhydrocarbon radicals containing on the average 16 to 18 carbon atoms.The laboratory runs were carried out as described in Example IV.

                  TABLE III                                                       ______________________________________                                             Sol. A.sup.a                                                                          Sol. R.sup.b                                                                          Crude Reaction                                                                              Corrosion                                                                             Pitting                            Run  (g)     (g)     Oil   Time (hrs)                                                                            Rate (mpy)                                                                            Index                              ______________________________________                                        12   0.1     0.4     .sup. NBU.sup.c                                                                     23      0.7     0.05                               13   0.4     0.1     NBU   23      2.6     0.1                                14   0.2     0.3     NBU   20.5    3.8     0.4                                15   0.3     0.2     NBU   21      2.2     0.6                                16   0.2     0.3     NBU   23.5    2.0     0.3                                17   0.3     0.2     NBU   7       0.46    0.2                                18   0.4     0.1     NBU   22      5.2     0.8                                19   0.3     0.2     NBU   22      0.75    0.3                                20   0.3     0.2     NBU   20      0.80    0.01                               21   0.15    0.1     .sup. NBU.sup.d                                                                     22.5    0.08    0.02                               22   0.45    0.13    Tor.sup.d                                                                           21      0.02    0                                  23   None    None    Te    20.7    110     0                                  ______________________________________                                         .sup.a The amine solution (Solution A) was prepared by mixing 1 part by       weight of the amine with 1 part by volume of alcohol and l part by volume     of xylene, e.g., 5 g of Duomeen T with 5 mL of methanol and 5 mL of           xylene.                                                                       .sup.b The resin solution (Solution R) was prepared by mixing 3 parts by      weight of the epoxy resin with 1 part by volume of xylene, e.g., 30 g of      Epon 828 with 10 mL of xylene.                                                .sup.c North Burbank Unit crude oil used with NBU brine.                      .sup.d Tor crude oil used with synthetic North Sea water.                     .sup.e Teesside (mixed crude oil from North Sea complex) crude oil with       synthetic North Sea water.                                               

EXAMPLE VIII

Laboratory runs were performed to demonstrate the effect of varying themolar ratio of the amine component with respect to the epoxy resincomponent. Selected ratios were tested in a series of runs and theresults summarized in Table IV. The runs were carried out essentially asdescribed in Example IV above. The runs were carried out in the presenceof 950 mL of synthetic North Sea water and 50 mL Teesside crude oilunder a CO₂ stream at 49° C. for 20 hours.

                                      TABLE IV                                    __________________________________________________________________________    Corrosion Inhibition in Duomeen-T/Epon 828                                    Systems With Selected Amine:Epoxy Molar Ratios                                                           20 Hr. Test Results                                   Sol. A                                                                            Sol. R                                                                            Vol. Ratio                                                                           Eq. Ratio                                                                          Ratio                                                                             Corrosion                                                                           Pitting                                      Run                                                                              (mL).sup.a                                                                        (mL).sup.b                                                                        Sol. A/Sol. R                                                                        A/R  (A/R)                                                                             Rate (mpy)                                                                          Index                                        __________________________________________________________________________    1  0.1 0.05                                                                              2      2.46 1.64                                                                              0     0.01                                         2  0.1 0.1 1      1.25 0.83                                                                              0.01  0.01                                         3  0.1 0.2 0.5    0.62 0.41                                                                              0.08  0.03                                         4  0.1 0.3 0.33   0.42 0.28                                                                              0.31  0.01                                         5  0.1 0.4 0.25   0.31  0.204                                                                            0.22  0.02                                         6  0.1 0.7 0.14   0.18  0.118                                                                            0.90  0.15                                         7  0.2 0.05                                                                              4      4.94 3.29                                                                              0.01  0                                            8  0.2 0.1 2      2.49 1.66                                                                              0.03  0.01                                         9  0.2 0.2 1      1.23 0.82                                                                              0.10  0.03                                         10 0.2 0.6 0.33   0.41  0.275                                                                            0.15  0.02                                         11 0.2 1.4 0.14   0.18  0.118                                                                            0.20  0.03                                         12 0.2 2.0 0.1    0.12  0.0824                                                                           4.6   2.5                                          __________________________________________________________________________     .sup.a Solution A was prepared by mixing equal weights of xylene, methano     and Duomeen T.                                                                .sup.b Solution R was prepared by mixing 10 parts by weight of Epon 828       with 20 parts by weight of xylene.                                       

Referring to the results tabulated in Table IV, the best results wereobtained in systems having a molar ratio of amine to resin varying overthe range of 0.41:1 to 3.29:1 (see runs 1, 2, 3, 7, 8, 9). Thecorresponding volume ratios of the amine solution to the resin solutionin these runs varied over the range of 0.5:1 to 4:1. In the lesseffective systems (runs 4, 5, 6, 10, 11, 12), the molar ratios of theamine to resin varied over the range of 0.08:1 to 0.28:1. Thecorresponding volume ratios of the amine solution to the resin solutionin these latter runs varied over the range of 0.1:1 to 0.33:1.

EXAMPLE IX

A series of laboratory corrosion inhibition tests were carried out in 1liter Erlenmeyer flasks equipped with magnetic stirring bars underlaboratory conditions designed to simulate corrosive environmentsencountered in field drilling sites.

A charge of 100 ml. of kerosene and 900 ml. of synthetic brine(CaCl₂.2H₂ O 85.07_(g), MgCl₂.6H₂ O 39.16 g, NaCl 2025.56 g alldissolved in 5 gallons of distilled water) was used in each run. Astream of carbon dioxide was bubbled through the solution during eachtest to maintain the mixture nearly saturated with CO₂. A carbon steelprobe was suspended in the stirred kerosene-synthetic brine mixture andmaintained at approximately 120° F. for approximately 1 hour followedthereafter by the addition of a mixture of various components which werebeing tested for their combined corrosion inhibiting qualities.

The components being tested for corrosion inhibition were added in thefollowing order: amine in xylene (50:50), an alcohol, and epoxy inxylene. The rate of corrosion and pitting index was determined using aCorrater® monitoring system available from Rohrback Instrumentsaccording to the manufacturer's instructions on an hourly basis asindicated. In this experiment methanol was the alcohol tested.

                  TABLE V                                                         ______________________________________                                                Inhibitor Concentration                                                         25      100        200   500                                                  PPM     PPM        PPM   PPM                                        Hours     MPY     MPY        MPY   MPY                                        ______________________________________                                        0.00      55.26   109.23     112.95                                                                              96.13                                      1.01      74.81   144.27     145.34                                                                              128.62                                     2.02      .10     8.25       14.27 15.90                                      3.02      .28     3.29       9.85  12.53                                      4.02      .13     1.42       8.14  12.54                                      5.03      .07     .86        7.03  12.20                                      6.03      .02     .42        6.01  12.75                                      7.03      .04     .22        5.79  13.67                                      8.04      .01     .17        6.09  13.49                                      9.04      .01     .09        5.30  12.27                                      10.05     .02     .05        5.44  11.45                                      11.05     .01     .03        7.35  11.57                                      12.05     .01     .09        3.92  11.27                                      13.06     .01     .03        2.43  10.62                                      14.06     .01     .02        1.56  9.75                                       15.06     .01     .04        1.09  9.67                                       16.07     .01     .03        .71   9.75                                       17.07     .01     .01        .48   10.77                                      18.08     .01     .01        .25   10.55                                      19.08     .01     .01        .10   9.05                                       20.08     .01     .03        .06   8.86                                       21.09     .01     .01        .03   9.24                                       22.09     .01     .01        .04   10.14                                      23.09     .01     .01        .89   8.93                                       24.10     .01     .01        .95   8.54                                       25.10     .01     .01        6.57  7.67                                       ______________________________________                                    

Table V demonstrates that methanol is a very effective component inreducing the corrosion rate in combination with an amine, hydrocarbondiluent, and epoxide.

EXAMPLE X

A series of laboratory corrosion inhibition tests were carried as setforth in Example IX utilizing ethanol as the alcohol.

Table VI presents the results of the effect of ethanol on a corrosioninhibiting mixture composed of an amine, hydrocarbon diluent andepoxide.

                                      TABLE VI                                    __________________________________________________________________________    Effectiveness of Ethanol in the Inhibitor.sup.a, b, c                                  Epoxy                                                                             Amine                                                                     in  in            Inhibitor                                                                          Corrosion                                     Run      Xylene                                                                            Xylene                                                                            Alcohol   used Rate at                                       No.                                                                              Alcohol                                                                             (ml)                                                                              (ml)                                                                              (ml) (wt. %)                                                                            (ppm)                                                                              24 hrs (mpy)                                  __________________________________________________________________________    1  Ethanol                                                                             0.45                                                                              1.2 0.60 25.5  25  0.17                                          2  Ethanol                                                                             0.45                                                                              1.2 0.60 25.5 100  0.90                                          3  Control A                                                                           0.45                                                                              1.2 0.0  0.0  100  7.56                                          4  Control B                                                                           0.0 0.0 0.0  0.0  --   226.14                                        __________________________________________________________________________     .sup.a Tests were carried out in the presence of 900 ml brine, 100 ml         kerosene and CO.sub.2 stream at 120° F.                                .sup.b The order of the components in the inhibitor added is as follows:      Amine in xylene (50:50)  Alcohol  Epoxy.                                      .sup.c Amine = Ntallow-1,3-propanediamine.                               

Table VI demonstrates that the addition of ethanol to a corrosioninhibiting mixture is effective in the reduction of the corrosion rate.

EXAMPLE XI

A series of laboratory corrosion inhibition tests were carried out asset forth in Example IX. Table VII presents the results of the effect ofisopropanol on a corrosion inhibiting mixture composed of an aminehydrocarbon diluent and epoxide.

                                      TABLE VII                                   __________________________________________________________________________    Effectiveness of Isoprooanl in the Inhibitor.sup.a, b, c                                Epoxy                                                                             Amine                                                                     in  in            Inhibitor                                                                          Corrosion                                    Run       Xylene                                                                            Xylene                                                                            Alcohol   used Rate at                                      No.                                                                              Alcohol                                                                              (ml)                                                                              (ml)                                                                              (ml) (wt. %)                                                                            (ppm)                                                                              24 hrs (mpy)                                 __________________________________________________________________________    1  Isopropanol                                                                          0.45                                                                              1.2 0.60 25.5  25  8.47                                         2  Isopropanol                                                                          0.45                                                                              1.2 0.60 25.5 100  6.13                                         3  Control A                                                                            0.45                                                                              1.2 0.0  0.0  100  7.56                                         4  Control B                                                                            0.0 0.0 0.0  0.0  --   226.14                                       __________________________________________________________________________     .sup.a Tests were carried out in the presence of 900 ml brine, 100 ml         kerosene and CO.sub.2 stream at 120° F.                                .sup.b The order of the components in the inhibitor added is as follows:      Amine in xylene (50:50)  Alcohol  Epoxy.                                      .sup.c Amine = Ntallow-1,3-propanediamine.                               

Table VII demonstrates that the addition of isopropanol on a corrosioninhibiting mixture is not effective in the reduction of the corrosionrate.

EXAMPLE XII

A series of laboratory corrosion inhibition tests were carried out asperformed in Example IX. Table VIII presents the results of theeffectiveness of the inhibitor solution composed of n-butanol, amine,hydrocarbon diluent, and epoxide at different concentrations.

                  TABLE VIII                                                      ______________________________________                                        n-butanol, Amine, Hydrocarbon Diluent, and Epoxide                                    Inhibitor Concentration                                                         25      100        200   500                                                  PPM     PPM        PPM   PPM                                        Hours     MPY     MPY        MPY   MPY                                        ______________________________________                                        0.00      125.63  98.69      78.27 107.40                                     1.01      135.36  129.95     127.67                                                                              126.58                                     2.02      2.71    3.62       4.22  19.67                                      3.02      1.57    .96        2.11  9.03                                       4.02      .99     .59        .98   5.76                                       5.03      .77     .24        .39   4.38                                       6.03      .38     .19        .55   3.62                                       7.03      .42     .13        .43   3.47                                       8.04      .24     .11        .53   3.35                                       9.04      .20     .08        .29   3.28                                       10.05     .16     .06        .26   3.31                                       11.05     .16     .04        .33   3.46                                       12.05     .10     .03        .30   3.49                                       13.06     .11     .02        .14   3.00                                       14.06     .10     .03        .18   3.59                                       15.06     .08     .02        1.10  3.79                                       16.07     .11     .02        .43   3.63                                       17.07     .09     .03        .22   4.06                                       18.08     .11     .03        .14   4.00                                       19.08     .07     .02        .14   3.61                                       20.08     .08     .02        .14   3.31                                       21.09     .05     .03        .19   3.19                                       22.09     .06     .02        .14   3.00                                       23.09     .06     .03        .16   2.89                                       24.10     .06     .04        .12   3.22                                       25.10     .06     .02        .11   3.59                                       ______________________________________                                    

Table VIII demonstrates the effectiveness of n-butanol in combinationwith an amine, hydrocarbon diluent, and epoxide as a corrosioninhibitor.

EXAMPLE XIII

A series of laboratory corrosion inhibition tests were carried out asset forth in Example IX. Table IX presents the results of the effect oft-butanol on a corrosion inhibiting mixture composed of an amine,hydrocarbon diluent and epoxide.

                                      TABLE IX                                    __________________________________________________________________________    Effectiveness of t-butanol in the Inhibitor.sup.a, b, c                                Epoxy                                                                             Amine                                                                     in  in            Inhibitor                                                                          Corrosion                                     Run      Xylene                                                                            Xylene                                                                            Alcohol   used Rate at                                       No.                                                                              Alcohol                                                                             (ml)                                                                              (ml)                                                                              (ml) (wt. %)                                                                            (ppm)                                                                              24 hrs (mpy)                                  __________________________________________________________________________    1  t-butanol                                                                           0.45                                                                              1.2 0.60 25.9  25  16.51                                         2  t-butanol                                                                           0.45                                                                              1.2 0.60 25.9 100  17.23                                         3  Control A                                                                           0.45                                                                              1.2 0.0  0.0  100  7.56                                          4  Control B                                                                           0.0 0.0 0.0  0.0  --   226.14                                        __________________________________________________________________________     .sup.a Tests were carried out in the presence of 900 ml brine (specified      by National Association of Corrosion Engineers), 100 ml kerosene and          CO.sub.2 stream at 120° F.                                             .sup.b The order of the components in the inhibitor added is as follows:      Amine in xylene (50:50)  Alcohol  Epoxy.                                      .sup.c Amine = Ntallow-1,3-propanediamine.                               

Table IX demonstrates that the addition of t-butanol to a corrosioninhibiting mixture is not effective in reducing the corrosion rate.

EXAMPLE XIV

A series of laboratory corrosion inhibition tests were carried out asperformed in Example IX. Table X presents the results of theeffectiveness of n-hexanol, amine, hydrocarbon diluent, and epoxide atdifferent concentrations.

                  TABLE X                                                         ______________________________________                                        n-hexanol, Amine, Hydrocarbon Diluent, and Epoxide                                    Inhibitor Concentration                                                         25      100        200   500                                                  PPM     PPM        PPM   PPM                                        Hours     MPY     MPY        MPY   MPY                                        ______________________________________                                        0.00      97.98   121.59     65.69 113.23                                     1.01      120.44  146.36     105.96                                                                              126.09                                     2.02      3.94    21.40      3.40  2.21                                       3.02      1.10    9.90       1.30  .34                                        4.02      .37     5.85       .72   .11                                        5.03      .24     4.28       .50   .09                                        6.03      .11     3.59       .38   .07                                        7.03      .22     3.21       .33   .04                                        8.04      .15     2.84       .29   .04                                        9.04      .14     2.37       .26   .03                                        10.05     .16     2.33       .24   .03                                        11.05     .17     2.06       .21   .02                                        12.05     .09     1.90       .19   .02                                        13.06     .13     1.69       .19   .01                                        14.06     .15     1.73       .19   .01                                        15.06     .19     1.61       .14   .01                                        16.07     .09     1.50       .17   .02                                        17.07     .13     1.39       .14   .01                                        18.08     .07     1.35       .15   .01                                        19.08     .10     1.50       .13   .01                                        20.08     .12     1.46       .12   .01                                        21.09     .21     1.53       .12   .01                                        22.09     .16     1.46       .10   .01                                        23.09     .10     1.21       .07   .01                                        24.10     .08     1.07       .07   .01                                        25.10     .17     .96        .07   .01                                        ______________________________________                                    

Table X demonstrates the effectiveness of n-hexanol in combination withan amine, hydrocarbon diluent, and epoxide as a corrosion inhibitor.

EXAMPLE XV

The following example provides Table XI which is a compilation of thedata presented in Example XI-XIV.

Table I provides a comparison of the effect of methanol, ethanol,isopropanol, n-butanol, t-butanol, and n-hexanol on a corrosioninhibiting mixture composed of an amine, hydrocarbon diluent andepoxide.

                                      TABLE XI                                    __________________________________________________________________________    Effectiveness of Alcohol in the Inhibitor.sup.a, b, c                                   Epoxy                                                                             Amine                                                                     in  in            Inhibitor                                                                          Corrosion                                    Run       Xylene                                                                            Xylene                                                                            Alcohol   used Rate at                                      No.                                                                              Alcohol                                                                              (ml)                                                                              (ml)                                                                              (ml) (wt. %)                                                                            (ppm)                                                                              24 hrs (mpy)                                 __________________________________________________________________________     1 Methanol                                                                             0.45                                                                              1.2 0.25 12.7  25  0.13                                          2 Methanol                                                                             0.45                                                                              1.2 0.25 12.7 100  0.22                                          3 Methanol                                                                             0.45                                                                              1.2 0.6  25.9  25  0.01                                          4 Methanol                                                                             0.45                                                                              1.2 0.6  25.9 100  0.01                                          5 Methanol                                                                             0.45                                                                              1.2 1.40 45.0  25  0.03                                          6 Methanol                                                                             0.45                                                                              1.2 1.40 45.0 100  0.76                                          7 Ethanol                                                                              0.45                                                                              1.2 0.60 25.5  25  0.17                                          8 Ethanol                                                                              0.45                                                                              1.2 0.60 25.5 100  0.90                                          9 Isopropanol                                                                          0.45                                                                              1.2 0.60 25.5  25  8.47                                         10 Isopropanol                                                                          0.45                                                                              1.2 0.60 25.5 100  6.13                                         11 n-Butanol                                                                            0.45                                                                              1.2 0.60 26.3  25  0.06                                         12 n-Butanol                                                                            0.45                                                                              1.2 0.60 26.3 100  0.02                                         13 t-Butanol                                                                            0.45                                                                              1.2 0.60 25.9  25  16.51                                        14 t-Butanol                                                                            0.45                                                                              1.2 0.60 25.9 100  17.23                                        15 n-Hexano1                                                                            0.45                                                                              1.2 0.60 26.3  25  0.17                                         16 n-Hexanol                                                                            0.45                                                                              1.2 0.60 26.3 100  0.96                                         17 Control A                                                                            0.45                                                                              1.2 0.0  0.0  100  7.56                                         18 Control B                                                                            0.0 0.0 0.0  0.0  --   226.14                                       __________________________________________________________________________     .sup.a Tests were carried out in the presence of 900 ml brine, 100 ml         kerosene and CO.sub.2 stream at 120° F.                                .sup.b The order of the components in the inhibitor added is as follows:      Amine in xylene (50:50)  Alcohol  Epoxy in xylene.                            .sup.c Amine = Ntallow-1,3-propanediamine.                               

As shown by the last column of Table XI, methanol was the most effectivealcohol over a broad range of concentration in lowering the corrosionrate in these tests. Table XI demonstrates that the addition of methanolsignificantly reduces the rate of corrosion observed when combined withan amine, hydrocarbon diluent and epoxide (comparing the control tomethanol).

EXAMPLE XVI

A series of laboratory corrosion inhibition tests were carried out asdescribed in Example IX. However, in this set of experiments, the amineutilized in the corrosion inhibitors were varied in each test. The rateof corrosion and pitting index was determined using a Corrater®monitoring system available from Rohrback Instruments according to themanufacturer's guidelines.

                                      TABLE XII                                   __________________________________________________________________________    Effectiveness of Amines in the Inhibitor.sup.a, b                                                   Epoxy in                                                                           Amine in  Inhibitor                                                                          Rate of                             Run                   Xylene                                                                             Xylene                                                                             Alcohol.sup.c                                                                      Used Corrosion                                                                           Pitting                       No.                                                                              Amine              (ml) (ml) (ml) (ppm)                                                                              MPY   Index                         __________________________________________________________________________    1  Cocoamine          0.45 1.2  0.6       0.5   0.85                          2  N-coco-1,3-propanediamine                                                                        0.45 1.2  0.6       1.2   0.7                           3  N-tallow-1,3-propanediamine diacetate                                                            0.45 1.2  0.6       3.6   2.8                           4  Trimethyltallow ammonium chloride                                                                0.45 1.2  0.6       2.8   3.0                           5  Trimethylcoco ammonium chloride                                                                  0.45 1.2  0.6       3.0   3.7                           6  Control.sup.d                          110   5.0                           __________________________________________________________________________     .sup.a The tests were carried out in the presence of 50 ml Ekofisk crude      oil and 950 ml Ekofisk syn. water and under carbon dioxide stream at          40° C. for 20 hours.                                                   .sup.b The order of the components in the inhibitor added is as follows:      Amine in xylene (50:50)  Alcohol  Epoxy in xylene.                            .sup.c The alcohol utilized in these tests was methanol.                      .sup.d The no amine and epoxy were present in the Control.               

As demonstrated by Table XII, cocoamine, tallowamine and N-coco-1,3diaminopropane are more effective in lowering the corrosion rate inthese tests than other monoamines and diamines such asN-tallow-1,3-propanedianime diacetate and the quarternary amines,trimethyltallowammonium chloride and trimethylcocoammonium chloride.Table XII further demonstrates that cocoamine, tallowamine andN-coco-1,3 diaminopropane contribute significantly to the reductions ofcorrosion in a corrosion inhibiting composition composed of an amine,alcohol, epoxy and a hydrocarbon diluent.

That which is claimed is:
 1. A method for treating metal surfaces ofdrilling equipment in a well for the recovery of natural fluids from asubterranean reservoir, the method comprising injecting a compositioncomprising an epoxy resin, a curing agent selected from the groupconsisting of N-coco-1,3 diaminopropane, tallowamine and cocoamine, forthe epoxy resin present in an amount such that the equivalent ratio ofthe curing agent to the epoxy resin is from about 1.5:1 to about 5:1, anaromatic hydrocarbon diluent present in at least an amount sufficient tomaintain the composition in an essentially fluid state, and an alcoholselected from the group consisting of methanol, ethanol, 1-propanol,2-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol andcombinations of any two or more thereof, present in an amount of about10 to about 60 weight percent of the composition into the well andallowing the composition to contact the metal surfaces for a timesufficient to form a corrosion-inhibiting film thereon.
 2. The method ofclaim 1 for inhibiting corrosion of metal surfaces of drilling equipmentin a well for the recovery of natural fluids from a subterraneanreservoir, comprising the steps of:(a) stopping production of thenatural fluids; (b) injecting the composition into the well, and (c)returning the well to production, thereby causing the composition to bereturned with the natural fluids and to be deposited as acorrosion-inhibiting film en route on metal surfaces with which it comesin contact.
 3. A method according to claim 2 in which the drillingequipment includes tubing within a well casing, the method furthercomprising injecting the composition between the tubing and casing,circulating the composition through the tubing and between the tubingand casing for a time at least sufficient to form a corrosion-inhibitingfilm thereon before returning the well to production.
 4. The method ofclaim 1 in which the composition is forced down the wall using a drivefluid.
 5. The method of claim 2 in which at least a portion of the wellis at a temperature of at least about 300° F. and a pressure of at leastabout 6000 psig.
 6. The method of claim 1 in which the aromatichydrocarbon diluent is xylene.
 7. The method of claim 1 in which thealcohol is present in an amount of about 20 to 30 weight percent, basedon the weight of the composition.
 8. The method of claim 1 in which theamine:epoxy equivalent ratio in the composition is about 1.5:1.
 9. Amethod for treating metal surfaces of drilling equipment in a well forthe recovery of natural fluids from a subterranean reservoir, the methodcomprising injecting a composition comprising:(a) an epoxy resin havingmore than one vicinal epoxide group per molecule; (b) an amine curingagent selected from the group consisting of N-coco-1,3-diaminopropane,tallowamine and cocoamine for the epoxy resin, the curing agent andepoxy being present in an equivalent ratio of from about 1.5:1 to about5:1; (c) a hydrocarbon diluent present in an amount to maintain thecomposition in an essentially fluid state; and (d) an alcohol selectedfrom the group consisting of methanol, ethanol, 1-propanol, 2-propanol,n-butanol, n-pentanol, n-hexanol, n-heptanol, and combinations of anytwo or more thereof, present in an amount of about 10 to about 60 weightpercent, based on the weight of the composition, into the well andallowing the composition to contact the metal surfaces for a timesufficient to form a corrosion-inhibiting film thereon.
 10. The methodof claim 9 for inhibiting corrosion of metal surfaces of drillingequipment in a well for the recovery of natural fluids from asubterranean reservoir, comprising the steps of:(a) stopping productionof the natural fluids; (b) injecting the composition into the well; and(c) returning the well to production, thereby causing the composition tobe returned with the natural fluids and to be deposited as acorrosion-inhibiting film en route on metal surfaces with which it comesin contact.
 11. The method of claim 10 in which the drilling equipmentincludes tubing within a well casing, the method further comprisinginjecting the composition between the tubing and casing, circulating thecomposition through the tubing and between the tubing and casing for atime at least sufficient to form a corrosion-inhibiting film thereonbefore returning the well to production.
 12. The method of claim 9 inwhich the composition is forced down the well using a drive fluid.